There are actually a number of data models that the relational model doesn't handle well, and it's unclear if it's really even the best model. Back when I was i

There are actually a number of data models that the relational model doesn't handle well, and it's unclear if it's really even the best model. Back when I was in database research most of our projects focused on domains where the relational model was not a good fit. Some examples of unnatural mappings to the relational model include: - Documents - Spatio-temporal - Graphs - K/V - Trees - CRDTS - Images - Arrays I'm sure there are plenty of others but those come to mind first. Most DB researchers I know would argue that if any database model is equivalent to the lambda calculus it would be graph theoretic model, because all other models can be expressed by graphs, but other models cannot universally express the graph model.